THE JURASSIC ANTALO LIMESTONE, MEKELLE BASIN, NORTHERN ETHIOPIA

Based on detailed lithofacies and microfacies data, shallow to deep marine homoclinal carbonate ramp, has been deduced for the Antalo Limestone of the Mekelle Basin. Stable oxygen and carbon isotopes also showed marine environments for the studied limestone samples that were subjected to deep burial diagenesis. The direct porosity-permeability measurements showed very low values, which signified the destruction of the original depositional porosities due to lithification. The lowstand systems tract (LST) of the second depositional sequence (DS2) and the highstand systems tract (HST) of the fourth depositional sequence (DS4), comprised potential storage horizons, with significant cavernous and solution-enlarged porosities. The source rock parameters indicate poor petroleum generating potential with over-mature, dry-gas prone kerogen. A Callovian ¿ Tithonian age has been deduced for the Antalo Limestone based on the recovered benthic foraminifera, dasyclad green algae, brachiopods and calpionellids. The geological evolution carbonate ramp platform in the Mekelle Basin has been deduced to be controlled by series of platform margin retreats and advances during Callovian ¿ Tithonian.